JP5245123B2 - Organic photoelectric conversion element, solar cell, and optical sensor array - Google Patents

Description

  The present invention relates to a bulk heterojunction photoelectric conversion element, a solar cell using the photoelectric conversion element, and an optical array sensor.

  The present invention relates to a bulk heterojunction organic photoelectric conversion element, a solar cell using the photoelectric conversion element, and an optical array sensor.

  Due to the recent rise in fossil energy, a system that can generate electric power directly from natural energy has been demanded. Solar cells using monocrystalline, polycrystalline, or amorphous Si, compound-based solar cells such as GaAs and CIGS, or Dye-sensitized photoelectric conversion elements (Gretzel cells) have been proposed and put into practical use.

  However, the cost of generating electricity with these solar cells is still higher than the price of electricity generated and transmitted using fossil fuels, which has hindered widespread use. In addition, since heavy glass must be used for the substrate, reinforcement work is required at the time of installation, which is one of the causes that increase the power generation cost.

  For such a situation, a transparent electrode as proposed in Non-Patent Document 1 (A. Heeger Single) as a solar cell that may be able to achieve a power generation cost lower than the power generation cost by fossil fuel. A bulk heterojunction photoelectric conversion element sandwiching a bulk heterojunction layer in which an electron donor layer (p-type semiconductor layer) and an electron acceptor layer (n-type semiconductor layer) are mixed between the electrode and the counter electrode Proposed.

  Thus, as a photoelectric conversion element that can be formed by a cost-effective solution coating method without using an electrolytic solution, for example, as disclosed in Patent Document 1, an electron donor layer between a transparent electrode and a counter electrode Heterojunction (stacked) photoelectric conversion element sandwiching (p-type semiconductor layer) and electron acceptor layer (n-type semiconductor layer), or a p-type semiconductor polymer and n between a transparent electrode and a counter electrode A bulk heterojunction photoelectric conversion element has been proposed in which a bulk hetero layer in which a uniform semiconductor material is uniformly mixed is formed.

  The operation principle of these photoelectric conversion elements will be described. First, excitons generated by photoexcitation move from the p-type semiconductor layer to the interface of the n-type semiconductor layer, and the excitons donate electrons to the electron acceptor layer. Thus, holes are generated in the p-type semiconductor layer and electrons are generated in the n-type semiconductor layer. Then, due to the internal electric field, holes pass through the p-type semiconductor layer to one electrode, and electrons pass through the n-type semiconductor layer to the other electrode. As a result, a photocurrent is observed.

  These bulk heterojunction photoelectric conversion elements achieve a conversion efficiency exceeding 5% by using a long-wave organic polymer that efficiently absorbs the sunlight spectrum (for example, the non-patent document). Reference 1).

  While the efficiency has been improved, it is necessary to continue to exhibit predetermined performance over a long period of time for practical use, and it is essential to improve the life. However, in Non-Patent Document 1 described above, under light irradiation for 100 hours, However, it is still not sufficient as described that the efficiency has decreased to 60%.

  In the non-patent document 2, the present inventors compare poly (3-hexylthiophene) (hereinafter referred to as P3HT), which is a p-type semiconductor material that has been conventionally used, with PCBM, which is an n-type semiconductor material, as a single unit. It was noted that the mobility was reported to be higher.

  That is, excitons are generated by light absorption in the bulk heterojunction layer, and equal amounts of holes and electrons are generated at the interface between the p-type semiconductor layer and the n-type semiconductor layer. This means that holes are not efficiently extracted due to low mobility, and most of the generated holes are trapped in the p-type semiconductor layer and converted to heat and deactivated. The present inventors presume that the presence of such a trap is the cause of deterioration of the bulk heterojunction photoelectric conversion element.

  From this point of view, polymer materials such as P3HT and polythiophene-thienothiophene copolymers that are currently used as standard in bulk heterojunction devices are obtained by polymerizing halogen-containing monomers ( Non-patent document 3), however, there is a possibility that metal atoms such as halogen atoms and tin, or metal compounds used for the polymerization catalyst may remain at the polymerization terminals. Therefore, it is estimated that these sites are carrier traps because they cannot be completely removed and must be used for the device. Furthermore, it is generally said that a high molecular material has a distribution in molecular weight, and therefore has lower crystallinity and lower mobility than a low molecular material.

Therefore, the present inventors do not use a high molecular material that is difficult to purify and has low mobility, but a low molecular weight organic compound having any structure as a p-type semiconductor material that has high mobility and can easily remove impurities that form carrier traps. It was examined whether a long-life organic photoelectric conversion element could be obtained by using a compound. And, it has a rigid and stable condensed ring structure, and it is possible to obtain a compound with higher crystallinity and mobility by keeping the conjugate length necessary and sufficient to absorb sunlight, and further, carrier trap at the molecular end. We examined from the idea that the low durability, which was a problem of organic photoelectric conversion elements, could be solved by eliminating potential sites.
Japanese Patent No. 40671115 Science, vol. 317 (2007), p222 Appl. Phys. Lett. , Vol. 87 (2005), p132105 Nature Material, (2006) vol. 5, p328

  This invention is made | formed in view of the said subject, The objective is to provide a highly durable organic photoelectric conversion element, the solar cell using this organic photoelectric conversion element, and an optical array sensor.

  The above object of the present invention is achieved by the following configurations.

1. Between the cathode and the anode, the organic photoelectric conversion element characterized by containing a low-molecular compound that is represented by the following general formula (3).

〔式中、Ｚは、置換若しくは無置換の、５員若しくは６員の芳香族環、またはこれらが縮合した縮合芳香族環を形成するに必要な原子群を表し、Ｒ _１ およびＲ _２ は、各々水素原子、ハロゲン原子、置換若しくは無置換の、アルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、シクロアルキル基、シリル基、エーテル基、チオエーテル基、またはアミノ基を表し、更にＲ _１ およびＲ _２ が互いに結合して環構造を形成しても良い。〕
２．前記一般式（１）で表される部分構造Ａ _１ が、下記一般式（２）で表される部分構造であることを特徴とする前記１に記載の有機光電変換素子。

〔式中、Ｒ _３ 〜Ｒ _６ は、各々水素原子、ハロゲン原子、置換または無置換のアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、シクロアルキル基、シリル基、エーテル基、チオエーテル基、またはアミノ基を表し、更にはＲ _３ およびＲ _５ 、またはＲ _４ およびＲ _６ が互いに結合して環構造を形成しても良い。〕 [ Wherein , A ₁ is a partial structure represented by the following general formula (1), and A ₂ and A ₃ are substituted or unsubstituted thiazole ring, pyrazole ring, imidazole ring, thiadiazole ring, oxadi An azole ring, a triazole ring, or a condensed ring structure containing these is represented. p, q, and r represent an integer of 1 to 4, and s represents an integer of 0 to 4. ]

[In the formula, Z represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, or a group of atoms necessary to form a condensed aromatic ring obtained by condensing them, and R ₁ and R ₂ are: Each represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, or amino group, and R ₁ and R ₂ may be bonded to each other to form a ring structure. ]
2. The organic photoelectric conversion element according to the 1 partial structures A ₁ represented by the general formula (1), characterized in that a partial structure represented by the following general formula (2).

[Wherein R _{3 to} R ₆ are each a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a cycloalkyl group, a silyl group, an ether group, or a thioether. Represents a group or an amino group, and R ₃ and R ₅ , or R ₄ and R ₆ may be bonded to each other to form a ring structure. ]

3. In the general formula (3), A ₂ is a thiazole ring, pyrazole ring, imidazole ring, thiadiazole ring, oxadiazole ring, triazole ring substituted with an alkyl group or a condensed ring structure containing these. The organic photoelectric conversion element according to 1 or 2 above.

4). Low molecular compound represented by the general formula (3) is, p-type semiconductor material and n-type bulk heterojunction layer semiconductor material are mixed, have the 1-3, characterized in that contained as a p-type semiconductor material the organic photoelectric conversion element according to an item or Re not.

5. 5. The organic photoelectric conversion element as described in 4 above, wherein the bulk heterojunction layer contains a fullerene derivative as the n-type semiconductor material .

6). In the chemical structural formula of the low molecular compound having the partial structure represented by the general formula (1), both ends of the conjugated chain having the maximum π conjugate length are both substituted with unsubstituted aromatic hydrocarbon rings. the organic photoelectric conversion device according to Izu Re or claim the 1 to 5, wherein the are.

7. The organic photoelectric conversion element according to any one of 4 to 6, wherein a bulk heterojunction layer containing the low molecular compound represented by the general formula (3) is formed by a solution process .

8). It consists of the organic photoelectric conversion element as described in any one of said 1-7, The solar cell characterized by the above-mentioned .

9. 8. An optical sensor array comprising the organic photoelectric conversion elements according to any one of 1 to 7 arranged in an array .

  According to the present invention, an organic photoelectric conversion element having high photoelectric conversion efficiency and durability, and a solar cell and an optical sensor array using the organic photoelectric conversion element can be provided.

  The present inventors have obtained a compound having a condensed ring structure and a conjugation length that is necessary and sufficient to absorb sunlight, and having higher crystallinity and higher mobility, and a carrier trap at the molecular end. By excluding a portion that can be obtained, an excellent organic photoelectric conversion element can be obtained.

  Hereinafter, the present invention will be described in detail.

[P-type semiconductor materials]
First, in the present invention, the low molecular weight compound means a single molecule having no distribution in the molecular weight of the compound. On the other hand, the polymer compound means an aggregate of compounds having a certain molecular weight distribution by reacting a predetermined monomer. However, in practical terms, when defining by molecular weight, a compound having a molecular weight of 3000 or less is preferably classified as a low molecular compound. More preferably, it is 2000 or less, More preferably, it is 1500 or less. The molecular weight can be measured by mass spectrum or gel permeation chromatography (GPC). In the present invention, in order to obtain a bulk heterojunction layer having high mobility, it is one feature that a low molecular weight compound having no molecular weight distribution and high crystallinity is used.

Next, the low molecular weight compound having the partial structure represented by the general formula (1) will be described.

  In the general formula (1), Z represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring or an atomic group necessary to form a condensed aromatic ring obtained by condensing these rings, and is condensed together with a thiophene ring. A condensed aromatic ring formed.

  Examples of the 5- or 6-membered aromatic ring formed by Z include thiophene ring, furan ring, pyrrole ring, pyrazole ring, thiazole ring, pyrazole ring, imidazole ring, thiadiazole ring, oxadiazole ring, triazole ring, phenyl Examples thereof include a ring, a naphthol ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, and a triazine ring, and a condensed aromatic ring in which these are condensed. By including such a condensed ring structure in the molecule, a rigid and stable semiconductor material for the power generation layer can be obtained. Further, by having at least a thiophene ring in the condensed ring structure, it has high mobility and high photoelectric conversion efficiency can be obtained.

R ₁ and R ₂ are each a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group And R ₁ and R ₂ may be bonded to each other to form a ring structure.

In the present invention, the “partial structure” in the low molecular weight compound having the partial structure represented by the general formula (1) or the partial structure represented by the general formula (1) is R in the general formula (1). _It means a mother nucleus structure in which a part of the aromatic ring represented by ₁ and R ₂ or Z is substituted with a bond, and these bonds are compounds further bonded to other chemical structures. Represent.

  Such a compound may act as a p-type semiconductor material or an n-type semiconductor material in the bulk heterojunction layer, but a thiophene compound generally has a higher hole mobility and is p-type. It preferably works as a semiconductor material. In general, p-type and n-type are classified as p-type materials that are mainly holes and n-type materials that are mainly electrons that contribute to electrical conduction in semiconductor materials.

Partial structure represented by the before following general formula (1) is contained at least two in the molecule. Before SL such as the general formula (1), by a plurality having chemical structure with high durability and high mobility structures in the molecule, it is possible to obtain a greater effect.

Further, in the chemical structure within the formula of the low molecular compound having a partial structure represented by the above general formula 6 Section (1), both terminals of a conjugated chain having a maximum of π conjugation length, unsubstituted co aromatic is to be substituted with group hydrocarbon ring, wherein a general formula (1) in partial structures one or more indicated, both ends of the conjugated chain having a maximum of π conjugation length in its chemical structure in formula no It means that it is a substituted aromatic hydrocarbon group. The aromatic hydrocarbon group, a benzene ring. In an organic photoelectric conversion element using a known π-conjugated polymer, since it is synthesized by a polymerization reaction, the terminal of the conjugated chain having the maximum conjugated length of the polymer is substituted with a halogen atom or a metal atom. However, in the present invention, it is presumed that higher durability can be obtained by substitution with the above-mentioned aromatic hydrocarbon ring, which does not become a substituent that can be a carrier trap .

The same applies to the general formula (2). The partial structure represented by the general formula (2) is a bond of a part of the substituents represented by R _{3 to} R ₆ in the general formula (2). It means that the bond is a compound bonded to another chemical structure. A photoelectric conversion device having higher conversion efficiency and durability by using a compound having a partial structure in which a condensed ring is formed between thiophene rings having high mobility as in the general formula (2) in a bulk heterojunction layer Can be obtained.

R ₃ and R ₄ are preferred as the position of the bond for incorporating the structure represented by the general formula (2) into the conjugated chain having the maximum π conjugate length in the chemical structural formula, and R ₃ and R ₄ replacement or unsubstituted thiazole ring, a pyrazole ring, an imidazole ring, a thiadiazole ring, an oxadiazole ring, that is substituted by one of the triazole ring preferred. This is because these five-membered aromatic rings have less steric hindrance between the aromatic rings, higher planarity between the two aromatic rings, and thus absorb light up to a long wave and higher mobility. It is because it is obtained.

The good preferable structures of the compounds used in the bulk heterojunction layer, a low molecular compound having a partial structure represented by the before following general formula (1) or (2) is represented by the above general formula (3) A compound. A ₁ in the general formula (3) represents the partial structure represented by the general formula (1) or (2), and R ₁ and R _{2 in} the general formula (1), or the aromatic ring represented by Z A compound in which a part or a part of the substituents represented by R _{3 to} R ₆ in the general formula (2) is substituted with a bond and bonded to A ₂ in the general formula (3) Represents. A ₂ and A ₃ represents a substituted or unsubstituted thiazole ring, a pyrazole ring, an imidazole ring, a thiadiazole ring, an oxadiazole ring, a triazole ring or a fused ring structure containing them.

With electron withdrawing aromatic ring such as these, the general formula (1) and an electron-donating aromatic ring and intramolecular charge transfer complexes such as thiophene-containing structure represented by (2) It is possible to form a photoelectric conversion material that can absorb a low band gap, that is, a long wave even if the conjugate length is relatively short.

Furthermore, heteroaryl groups represented by A _2, it is preferably substituted by an alkyl group. By substituting an alkyl group at this position, the solubility of the compound is improved, and it becomes easier to form a bulk heterojunction layer by a solution process. Moreover, there is an effect that the crystallinity of the compound is increased by using a so-called fastener effect in which alkyl chains try to pack each other, and higher photoelectric conversion efficiency can be obtained. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group, a pentyl group, a hexyl group, a 2-ethylhexyl group, an octyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group. In order to obtain the above-mentioned fastener effect, it is preferable to use a C6-C20 linear alkyl group (n-hexyl group, n-octyl group, n-dodecyl group, etc.).

Hereinafter, specific examples of the low molecular compound and reference and the compound represented by the general formula (3) according to the present invention, the present invention is not limited thereto. These compounds are disclosed in Non-Patent Document 3 and Synth. Met. Vol. 148 (2005), p195 and the like can be synthesized.

[N-type semiconductor materials]
The organic photoelectric conversion element of the present invention is preferably applied to a bulk heterojunction layer in which an n-type semiconductor material and a p-type semiconductor material are mixed, and the low molecular compound of the present invention may be used as the p-type semiconductor material. The material is not particularly limited. For example, fullerene, octaazaporphyrin, and the like, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic diimide, perylene tetra Examples thereof include aromatic carboxylic acid anhydrides such as carboxylic acid anhydrides and perylene tetracarboxylic acid diimides, and polymer compounds containing the imidized product thereof as a skeleton.

  However, when the material having a thiophene-containing fused ring of the present invention is used as a p-type semiconductor material, a fullerene derivative capable of efficient charge separation is preferable. Fullerene derivatives include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc. Partially by hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, etc. Examples thereof include substituted fullerene derivatives.

  Among them, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61-buty Rick acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, and cyclics such as US Pat. No. 7,329,709. It is preferable to use a fullerene derivative having a substituent and having improved solubility, such as fullerene having an ether group.

(Layer structure of organic photoelectric conversion element and solar cell)
FIG. 1 is a cross-sectional view showing a solar cell composed of a bulk heterojunction organic photoelectric conversion element. In FIG. 1, a bulk heterojunction type organic photoelectric conversion element 10 has a transparent electrode 12, a bulk heterojunction layer photoelectric conversion unit 14, and a counter electrode 13 sequentially stacked on one surface of a substrate 11.

  The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 that are sequentially stacked. In the present embodiment, since light that is photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light that is photoelectrically converted, that is, with respect to the wavelength of the light to be photoelectrically converted. It is a transparent member. As the substrate 11, for example, a glass substrate or a resin substrate is used. The substrate 11 is not essential. For example, the bulk heterojunction type organic photoelectric conversion element 10 may be configured by forming the transparent electrode 12 and the counter electrode 13 on both surfaces of the photoelectric conversion unit 14.

The transparent electrode 12 is an electrode that can transmit light that is photoelectrically converted in the photoelectric conversion unit 14, and is preferably an electrode that transmits light of 300 to 800 nm. Examples of the material include transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ , ZnO, fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO), and metals such as gold, silver, and platinum. A thin film or a nanoparticle / nanowire layer and a conductive polymer can be used.

  The counter electrode 13 may be made of metal (for example, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon, or the material of the transparent electrode 12, but is not limited thereto.

  In the bulk heterojunction type organic photoelectric conversion element 10 shown in FIG. 1, the photoelectric conversion unit 14 is sandwiched between the transparent electrode 12 and the counter electrode 13, but the pair of comb-like electrodes are arranged on one side of the photoelectric conversion unit 14. The back contact type organic photoelectric conversion element 10 may be configured such that the back contact type organic photoelectric conversion element 10 is disposed.

  The photoelectric conversion unit 14 is a layer that converts light energy into electric energy, and includes a bulk heterojunction layer in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

  As the p-type semiconductor material, the compound of the present invention is used. Further, for example, a known tetrabenzoporphyrin derivative or the like may be used in combination. And as an n-type semiconductor material, in order to implement | achieve comparatively high photoelectric conversion efficiency, a fullerene derivative is used, for example.

  As a method for forming a bulk heterojunction layer in which an electron acceptor and an electron donor are mixed, since the compound of the present invention is a low molecular compound, a vapor deposition method, a coating method (including a cast method and a spin coat method), etc. Any method may be used, but in the present invention, a coating method having excellent film forming cost is preferable.

  In order to improve the photoelectric conversion rate, the bulk heterojunction layer of the photoelectric conversion unit 14 is preferably annealed at a predetermined temperature during the manufacturing process and partially crystallized microscopically. As a result, the carrier mobility of the bulk heterojunction layer is improved and high efficiency can be obtained.

  In FIG. 1, light incident from the transparent electrode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the bulk heterojunction layer of the photoelectric conversion unit 14, and electrons move from the electron donor to the electron acceptor. Thus, a hole-electron pair (charge separation state) is formed. The generated electric charge is caused by an internal electric field, for example, when the work functions of the transparent electrode 12 and the counter electrode 13 are different, the electrons pass between the electron acceptors due to the potential difference between the transparent electrode 12 and the counter electrode 13, and the holes are , Passed between the electron donors and carried to different electrodes, and photocurrent is detected. For example, when the work function of the transparent electrode 12 is larger than the work function of the counter electrode 13, electrons are transported to the transparent electrode 12 and holes are transported to the counter electrode 13. If the magnitude of the work function is reversed, electrons and holes are transported in the opposite direction. In addition, by applying a potential between the transparent electrode 12 and the counter electrode 13, the transport direction of electrons and holes can be controlled.

  Returning to FIG. 1, the photoelectric conversion unit 14 may be composed of a single layer in which the electron acceptor and the electron donor are uniformly mixed, but the mixing ratio of the electron acceptor and the electron donor is changed. You may comprise by the changed multiple layer.

  Examples of a method for forming a bulk heterojunction layer in which an electron acceptor and an electron donor are mixed include a vapor deposition method and a coating method (including a casting method and a spin coating method). Among these, the coating method is preferable in order to increase the area of the interface where charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. After application, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and increase in mobility and longer absorption due to crystallization of the semiconductor material.

  The bulk heterojunction type organic photoelectric conversion element 10 includes the transparent electrode 12, the bulk heterojunction layer photoelectric conversion unit 14 and the counter electrode 13 which are sequentially stacked on the substrate 11, but is not limited thereto. For example, there are other layers such as a hole transport layer, an electron transport layer, a hole block layer, an electron block layer, or a smoothing layer between the transparent electrode 12 or the counter electrode 13 and the photoelectric conversion unit 14 and bulk hetero The junction type organic photoelectric conversion element 10 may be configured. FIG. 2 is a cross-sectional view showing another example of the layer structure of a bulk heterojunction type organic photoelectric conversion element. As shown in FIG. 2, a hole transport layer 17 is placed between the bulk heterojunction layer and the anode (usually the transparent electrode 12 side), and electrons are placed between the cathode (usually the counter electrode 13 side). By forming the transport layer 18, it is possible to more efficiently extract charges generated in the bulk heterojunction layer. Therefore, it is preferable to include these layers.

  As a material constituting these layers, for example, as the hole transport layer 17, PEDOT such as trade name BaytronP, polyaniline and its doped material, cyan compound described in WO2006019270, etc. Can be used. Note that electrons generated in the bulk heterojunction layer do not flow to the anode side in the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the bulk heterojunction layer. An electronic block function having a rectifying effect is provided. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function. As such a material, a triarylamine compound described in JP-A-5-271166 or a metal oxide such as molybdenum oxide, nickel oxide, or tungsten oxide can be used. Moreover, the layer which consists of a p-type semiconductor material single-piece | unit used for the bulk heterojunction layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

  As the electron transport layer 18, octaazaporphyrin, a p-type semiconductor perfluoro compound (perfluoropentacene, perfluorophthalocyanine, etc.) can be used. Similarly, a p-type semiconductor used for a bulk heterojunction layer. The electron transport layer having a HOMO level deeper than the HOMO level of the material is provided with a hole blocking function that has a rectifying effect so that holes generated in the bulk heterojunction layer do not flow to the cathode side. The Such an electron transport layer is also called a hole blocking layer, and it is preferable to use an electron transport layer having such a function. Examples of such materials include phenanthrene compounds such as bathocuproine, n-type semiconductor materials such as naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, and titanium oxide. N-type inorganic oxides such as zinc oxide and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used. A layer made of a single n-type semiconductor material used for the bulk heterojunction layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method.

  Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). FIG. 3 is a cross-sectional view showing a solar cell composed of an organic photoelectric conversion element including a tandem bulk heterojunction layer. In the case of the tandem configuration, the transparent electrode 12 and the first photoelectric conversion unit 14 are sequentially stacked on the substrate 11, the charge recombination layer 15 is stacked, the second photoelectric conversion unit 16, and then the counter electrode 13. By stacking layers, a tandem configuration can be obtained. The second photoelectric conversion unit 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion unit 14 or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. . The material of the charge recombination layer 15 is preferably a layer using a compound having both transparency and conductivity, such as transparent metal oxides such as ITO, AZO, FTO, and titanium oxide, Ag, Al, and Au. A very thin metal layer such as PEDOT: PSS or a conductive polymer material such as polyaniline is preferable.

  Moreover, it is preferable to seal by the well-known method so that the produced organic photoelectric conversion element 10 does not deteriorate with oxygen, moisture, etc. in the environment. For example, a method of sealing a cap made of aluminum or glass by bonding with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed and the organic photoelectric conversion element top 10 with an adhesive A method of bonding, a method of spin-coating an organic polymer material with high gas barrier properties (polyvinyl alcohol, etc.), a method of directly depositing an inorganic thin film with high gas barrier properties (silicon oxide, aluminum oxide, etc.), and a combination of these The method of laminating can be mentioned.

(Optical sensor array)
Next, an optical sensor array to which the bulk heterojunction type organic photoelectric conversion element 10 described above is applied will be described in detail. The optical sensor array is produced by arranging the photoelectric conversion elements in a fine pixel form by utilizing the fact that the bulk heterojunction type organic photoelectric conversion elements generate a current upon receiving light, and projected onto the optical sensor array. A sensor having an effect of converting an image into an electrical signal.

  FIG. 4 is a diagram showing the configuration of the photosensor array. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA ′ of FIG. 4A.

  In FIG. 4, the optical sensor array 20 is paired with a transparent electrode 22 as a lower electrode, a photoelectric conversion unit 24 that converts light energy into electric energy, and a transparent electrode 22 on a substrate 21 as a holding member. The counter electrode 23 is sequentially laminated. The photoelectric conversion unit 24 includes two layers, a photoelectric conversion layer 24b having a bulk heterojunction layer in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed, and a buffer layer 24a. In the example shown in FIG. 4, a total of six bulk heterojunction organic photoelectric conversion elements of 2 rows × 3 columns are formed.

  The substrate 21, the transparent electrode 22, the photoelectric conversion layer 24 b, and the counter electrode 23 have the same configuration and role as the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 in the bulk heterojunction photoelectric conversion element 10 described above. It is.

  For example, glass is used for the substrate 21, ITO is used for the transparent electrode 22, and aluminum is used for the counter electrode 23, for example. The low molecular weight exemplary compound 12 of the present invention is used for the p-type semiconductor material of the photoelectric conversion layer 24b, and bis-PCBM is used for the n-type semiconductor material, for example. The hole transport layer 24a is made of PEDOT (poly-3,4-ethylenedioxythiophene) -PSS (polystyrene sulfonic acid) conductive polymer (trade name BaytronP, manufactured by Stark Vitec). Such an optical sensor array 20 was manufactured as follows.

  An ITO film was formed on the glass substrate by sputtering and processed into a predetermined pattern shape by photolithography. The thickness of the glass substrate was 0.7 mm, the thickness of the ITO film was 200 nm, and the measurement area (light receiving area) of the ITO film after photolithography was 1 mm × 1 mm. Next, a PEDOT-PSS film was formed on the glass substrate 21 by spin coating (conditions: rotational speed = 1000 rpm, filter diameter = 1.2 μm). Thereafter, the substrate was heated in an oven at 140 ° C. for 10 minutes and dried. The thickness of the PEDOT-PSS film after drying was 30 nm.

  Next, a bulk heterojunction layer made of a 1: 1 mixture of Exemplified Compound 12 and Bis-PCBM is formed on the PEDOT-PSS film by spin coating (conditions: rotational speed = 500 rpm, filter diameter = 0.4 μm). ). After the formation of the bulk heterojunction layer, annealing was performed by heating in an oven at 140 ° C. for 30 minutes in a nitrogen gas atmosphere.

  Thereafter, a metal mask having a predetermined pattern opening was used to form, on the bulk heterojunction layer, 5 nm of lithium fluoride as a buffer layer and 100 nm of an aluminum layer as an upper electrode by a vapor deposition method.

  Thereafter, sealing was performed using an aluminum cap and a UV curable resin in a nitrogen atmosphere. The optical sensor array 20 was produced as described above.

  The manufactured photosensor array 20 having 2 rows × 3 columns of pixels is irradiated with light so that only the two pixels in the center column are exposed to light, and the 6 pixels are sequentially set to −0. When the current value was read by applying a voltage of 5 V, the current was observed only in the pixels that were exposed to light, and no current flowed in the pixels that were not exposed to light. Therefore, it was confirmed that the optical sensor array 20 operates as an optical sensor.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Preparation of Comparative Organic Photoelectric Conversion Element 1>
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 110 nm (sheet resistance 13 Ω / □) is obtained by using an ordinary photolithography technique and hydrochloric acid etching to have an electrode width of 2 mm and an interelectrode gap of 2 mm. To form a transparent electrode.

  The patterned transparent electrode was cleaned in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried by nitrogen blowing, and finally subjected to ultraviolet ozone cleaning.

  On this transparent substrate, Baytron PH510 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated with a film thickness of 30 nm, and then heat-dried at 140 ° C. for 10 minutes in the air.

  After this, the substrate was brought into the glove box and worked under a nitrogen atmosphere.

  First, the substrate was heat-treated at 180 ° C. for 3 minutes in a nitrogen atmosphere.

  A solution was prepared by dissolving 1.5 mass% of plexcores OS2100 manufactured by Plextronics as p-type semiconductor material and 1.5 mass% of bis-PCBM manufactured by Solenen as the n-type semiconductor material in chlorobenzene, and having a concentration of 0.45 μm. While being filtered through the above filter, spin coating was performed at 500 rpm for 60 seconds, then at 2200 rpm for 1 second, and dried at room temperature for 30 minutes.

Next, the substrate on which the series of organic layers was formed was placed in a vacuum deposition apparatus. The substrate was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 5 nm of lithium fluoride and 80 nm of Al were evaporated. Finally, the heating for 30 minutes was performed at 120 degreeC, and the comparative organic photoelectric conversion element 1 was obtained. The vapor deposition rate was 2 nm / second for all, and the size of the light receiving area was 2 mm □.

The obtained organic photoelectric conversion element 1 was sealed with an aluminum cap and a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) in a nitrogen atmosphere, and then taken out into the atmosphere to be a solar simulator. (AM1.5G) light was irradiated at an irradiation intensity of 100 mW / cm ² to measure voltage-current characteristics. The initial photoelectric conversion efficiency at this time is assumed to be 100, and the irradiation is continued for 24 hours at an irradiation intensity of 1 W / cm ² with a resistor connected between the anode and the cathode, and then the relative photoelectric conversion efficiency at 100 mW / cm ² is again measured. When the rate of decrease (%) (smaller is better) was evaluated, the efficiency after the durability test was 75% with respect to the initial value.

<Preparation of Organic Photoelectric Conversion Elements 2 to 6 of the Invention and Referenced >
In the production of the comparative organic photoelectric conversion element 1, the comparative organic photoelectric conversion element was changed except that the p-type semiconductor material was changed to the compound according to the present invention described in Table 1 and used as a reference instead of the plex core OS2100. In the same manner as in Example 1, organic photoelectric conversion elements 2 to 6 were obtained.

The obtained organic photoelectric conversion elements 2 to 6 were sealed in the same manner as the organic photoelectric conversion element 1 using an aluminum cap and a UV curable resin in a nitrogen atmosphere, and then taken out into the atmosphere to obtain a solar simulator (AM1). .5G) was irradiated at an irradiation intensity of 100 mW / cm ² to measure voltage-current characteristics. The initial photoelectric conversion efficiency at this time was set to 100, and after continuing irradiation for 24 hours at an irradiation intensity of 1 W / cm ² with a resistor connected between the anode and the cathode, the measurement value at 100 mW / cm ² was evaluated again. The relative reduction rate (%) of the photoelectric conversion efficiency after the durability test was calculated. The calculated values are shown in Table 1.

  As can be seen from Table 1, it can be seen that the organic photoelectric conversion element of the present invention exhibits excellent durability.

It is sectional drawing which shows the laminated constitution of the solar cell which consists of a bulk heterojunction type organic photoelectric conversion element. It is sectional drawing which shows the other example of a layer structure of a bulk heterojunction type organic photoelectric conversion element. It is sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with a tandem-type bulk heterojunction layer. It is a figure which shows the structure of an optical sensor array.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bulk heterojunction type organic photoelectric conversion element 11, 21 Substrate 12, 22 Transparent electrode 13, 23 Counter electrode 14, 16, 24 Photoelectric conversion part 15 Charge recombination layer 17 Hole transport layer 18 Electron transport layer 20 Photosensor array

Claims (9)

Between the cathode and the anode, the organic photoelectric conversion element characterized by containing a low-molecular compound that is represented by the following general formula (3).

[ Wherein , A ₁ is a partial structure represented by the following general formula (1), and A ₂ and A ₃ are substituted or unsubstituted thiazole ring, pyrazole ring, imidazole ring, thiadiazole ring, oxadi An azole ring, a triazole ring, or a condensed ring structure containing these is represented. p, q, and r represent an integer of 1 to 4, and s represents an integer of 0 to 4. ]

[In the formula, Z represents a substituted or unsubstituted 5-membered or 6-membered aromatic ring, or a group of atoms necessary to form a condensed aromatic ring obtained by condensing them, and R ₁ and R ₂ are: Each represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, or amino group, and R ₁ and R ₂ may be bonded to each other to form a ring structure. ] The organic photoelectric conversion element according to claim 1, the partial structure A ₁ represented by the general formula (1), characterized in that a partial structure represented by the following general formula (2).

[Wherein R _{3 to} R ₆ are each a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a cycloalkyl group, a silyl group, an ether group, or a thioether. Represents a group or an amino group, and R ₃ and R ₅ , or R ₄ and R ₆ may be bonded to each other to form a ring structure. ] In the general formula (3), A ₂ is a thiazole ring, pyrazole ring, imidazole ring, thiadiazole ring, oxadiazole ring, triazole ring substituted with an alkyl group, or a condensed ring structure containing these. The organic photoelectric conversion element according to claim 1 or 2. The low molecular compound represented by the general formula (3) is contained as a p-type semiconductor material in a bulk heterojunction layer in which a p-type semiconductor material and an n-type semiconductor material are mixed . the organic photoelectric conversion device according to Izu Re or claim. The organic photoelectric conversion device according to claim 4 , wherein the bulk heterojunction layer contains a fullerene derivative as the n-type semiconductor material . In the chemical structural formula of the low molecular compound having the partial structure represented by the general formula (1), both ends of the conjugated chain having the maximum π conjugate length are both substituted with unsubstituted aromatic hydrocarbon rings. the organic photoelectric conversion device according to Izu Re one of claims 1-5, characterized in that is. 7. The organic photoelectric conversion element according to claim 4, wherein the bulk heterojunction layer containing the low-molecular compound represented by the general formula (3) is formed by a solution process . It consists of an organic photoelectric conversion element as described in any one of Claims 1-7, The solar cell characterized by the above-mentioned . 8. An optical sensor array comprising the organic photoelectric conversion elements according to any one of claims 1 to 7 arranged in an array .

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